1. Field of the Invention
This invention relates, in general, to liquid cleaning apparatus and, more specifically, to deionized water cleaning of printed circuit boards.
2. Description of the Prior Art
Components are soldered to electrical printed circuit boards (PCB's) with the aid of solder fluxes which leave a residue on the board after the soldering process has been completed. For various reasons, it is desirable to remove the flux from the boards after the soldering process. Traditionally, volatile solvents have been widely used to wash solder flux from PCB's. However, such solvents can have negative environmental impacts and are being phased out in favor of other washing liquids.
With the recent use of water-based fluxes, it is possible to use water as the washing liquid for PCB's soldered with this type of flux. In order to keep the rinse water from contaminating outside waste water disposal systems, the water used for washing PCB's is passed through a series of filters to remove the contaminants from the water. This permits reuse of the same water in a closed-loop cleaning system. Deionizing the water also provides a method of purifying the water and allowing it to be recirculated again throughout the cleaning process. Such systems are currently in use at factories or shops where PCB's are soldered. Although such systems provide certain advantages over prior art systems, they may require large filter systems and a considerable amount of fixed plumbing to be installed at the factory location. Along with being dependent upon permanently installed filters, pumps, piping, etc., such systems are usually confined to a specific location on the factory floor. When the need to have a washing station at another location arises the traditional fixed systems are not very cost efficient in providing the new or alternate washing station. Therefore, it is desirable, and an object of this invention, to provide a PCB washing system which can be easily adapted for use at various locations throughout the factory.
U.S. Pat. No. 3,595,252, issued on Jul. 27, 1971, discloses a self-contained washing unit intended for use in washing scientific glassware with deionized water. This system includes a container housing, collection tank, pump, and deionizer which cooperate with each other to allow the water to recirculate between washing and purification operations. Although apparently useful for the intended application, there are significant differences between the structure of the patented device and the apparatus disclosed herein for washing PCB's.